Heat sterilized milk-added coffee beverage and method of suppressing precipitates in same

ABSTRACT

An economical process for producing a milk-added coffee beverage with an enhanced flavor in a process for producing a milk-added coffee beverage produced through a step of heat sterilization of coffee and milk as the main raw materials. The process includes adding a strongly basic substance and/or basic amino acid to the coffee component and conducting the heat sterilization after the milk component is admixed to the coffee component. Coagulation at the step of admixing milk component is prevented and precipitation which tends to arise after the heat sterilization is prevented with the use of a much smaller amount of emulsifier and thickening agent.

BACKGROUND OF THE INVENTION

The present invention relates to a milk-added coffee beverage producedthrough a step of heat sterilization using coffee and milk component asthe raw materials, and to a process for producing it. More specifically,it relates to a stable and rich-flavored milk-added coffee beverage inwhich precipitation that occurs after heat sterilization treatment isprevented, and to a process for producing it.

A wide variety of milk-added coffee beverage products (hereunderreferred to as “milk-added coffee beverages”) are known that areproduced through a step of heat sterilization using coffee and milkcomponents as the raw materials, and when classified according to thetype of container these include canned beverages, PET bottled beverages,cardboard packed beverages and the like.

The common production steps for milk-added coffee beverages, in the caseof canned milk-added coffee beverages for example, are “roasting”,“grinding”, “extraction”, “formulation”, “filtration”, “filling”,“rolling”, “sterilization”, “refrigeration” and “case packing”.

The “formulation” step is a critical step in terms of the quality ofproduct in the milk-added coffee beverage production process.Specifically, when milk is directly added to coffee extract, the acidicpH of the coffee extract causes the milk to coagulate. It has beencommon in the past to add sodium bicarbonate to milk-added coffeebeverages in order to prevent milk coagulation. Sodium bicarbonate isused because it is colorless and odorless, and has little effect onflavor.

The “sterilization” step is also a critical step in terms of the qualityof product in the milk-added coffee beverage production process. In thesterilization step, heat sterilization is usually carried out for 20minutes in a 250 g can at 125° C. (“Food Production/Distribution DataHandbook”, Japan Industry Research Institute Publication Center, p.720).However, milk-added coffee beverages tend to produce precipitation afterheat sterilization, and although such precipitation poses no problemwhatsoever in terms of the safety of the product, it considerablyimpairs the product value.

Adjustment in the amount of sodium bicarbonate added has been a commonmeans used to prevent these problems, but this alone does not provide asufficient anti-precipitation effect, and therefore addition of anemulsifier or thickening agent (stabilizer, thickener, etc.) has beennecessary. However, while addition of an emulsifier or thickening agentprovides an anti-precipitation effect, it is sometimes undesirable fromthe standpoint of the flavor of the milk-added coffee beverage, and hasalso raised the product cost. In addition, since a greater amount ofcoffee and milk components tends to result in easier precipitation afterheat sterilization, it is necessary to increase the amount of emulsifieror thickening agent, and this has led to problems of further flavorimpairment or cost increase. Depending on the formulation, even additionof an emulsifier or thickening agent fails to provide a sufficientanti-precipitation effect in many cases.

Japanese Unexamined Patent Publication HEI No. 7-184546 discloses aprocess for producing a stable coffee beverage which is characterized bysubjecting a coffee extract to both treatment with mannanase andaddition of alkali sodium or potassium salts, and particularly sodiumbicarbonate.

Also, Japanese Unexamined Patent Publication HEI No. 8-228686 disclosesa method of preventing precipitation of milk-added canned coffee whichis characterized by adding a mixed emulsifier comprising a combinationof emulsifiers each with a different HLB (hydrophilic-lipophilicbalance).

In addition, Japanese Unexamined Patent Publication HEI No. 11-313647discloses a method of preventing precipitation of milk-added cannedcoffee which is characterized by alkali-treating roasted coffee beansbefore extraction.

These methods all have their respective features, but an even simpler,more economical method has been desired.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide aneconomical method for preventing precipitation in milk-added coffeebeverages during admixture of the milk and after heat sterilization.

It is another object of the invention to provide a rich-flavoredmilk-added coffee beverage wherein precipitation during admixture ofmilk component and after heat sterilization is prevented.

It is yet another object of the invention to provide a milk-added coffeebeverage which is prepared by a process for production of milk-addedcoffee beverages involving heat sterilization after admixture of themilk component, wherein a strongly basic substance and/or a basic aminoacid is added before admixture of the milk component, in order toprevent precipitation during admixture of the milk and after the heatsterilization, and to reduce the amount of emulsifier or thickeningagent added which has been a cause of reduced flavor, as well as aprocess for its production.

The invention may be applied with particular advantages in productshaving a high content of coffee and milk components, to preventprecipitation after heat sterilization without increasing the amount ofadded emulsifier or thickening agent.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing the relationship between the amount of sodiumbicarbonate added (pH) and the degree of precipitation after heatsterilization, for an emulsifier-free canned milk-added coffee beverage.

FIG. 2 is a bar graph showing the degree of precipitation after heatsterilization with addition of both sodium bicarbonate and different pHadjusters in emulsifier-free canned milk-added coffee beverages.

FIG. 3 is a graph showing the relationship between the amount ofstrongly basic substance added (pH) and the degree of precipitationafter heat sterilization, for an emulsifier-free canned milk-addedcoffee beverage.

FIG. 4 is a bar graph showing the degree of precipitation after heatsterilization with addition of basic amino acids in emulsifier-freecanned milk-added coffee beverages.

DETAILED DESCRIPTION OF THE INVENTION

As a result of extensive research into the cause of precipitation inmilk-added coffee beverages after heat sterilization, for the purpose ofsolving the problems described above, the present inventors found,surprisingly, that sodium bicarbonate that has conventionally been usedfor pH adjustment to prevent coagulation during the milk-mixing step isthe major cause of precipitation during the heat sterilization step.Upon examining the mechanism of precipitation due to sodium bicarbonate,it was determined that precipitation of coffee and milk occurs becauseof a salting-out reaction due to sodium bicarbonate.

The present inventors then tried replacing all or a portion of thesodium bicarbonate with strongly basic substances and/or basic aminoacids, and completed the present invention upon determining that thiscan prevent coagulation during admixture of milk component and preventprecipitation after heat sterilization.

When using a strongly basic substance or a basic amino acid in amilk-added coffee beverage according to the invention, there is noadverse effect on the color, odor or taste, similar to sodiumbicarbonate. In fact, it is possible to reduce or eliminate the additionof emulsifier or thickening agent, which has been a cause of impairedflavor, and thereby produce a milk-added coffee beverage with a moresatisfactory flavor than conventional coffee beverages. A particularlynotable difference in flavor over the prior art method is achieved whensubstantially no sweetener component is added, so that a beverageexhibiting the original satisfactory flavor of milk-added coffeebeverages may be obtained together with an anti-precipitation effect.

The present invention will now be explained in detail.

According to the present invention, “milk-added coffee beverage” refersto a beverage product prepared using coffee and milk components as themain raw materials, through a step of heat sterilization. The type ofproduct is not particularly restricted, but mainly intended are“coffee”, “coffee beverages” and “coffee-added soft drinks” as definedby the “Fair Competition Guidelines on Labeling of Coffee and OtherBeverages” established in 1977. Beverages prepared from coffee as theraw material and having a milk solid content of at least 3.0% by weightfall under the “Fair Competition Guidelines on Labeling of DrinkingMilk” and are treated as “milk beverages”, but for the purpose of thepresent invention these will also be included as milk-containing coffeebeverages.

“Coffee component” refers to a solution containing coffee bean-derivedcomponents, of which there may be mentioned primarily coffee extracts,i.e., solutions obtained by extraction of roasted and ground coffeebeans using cold or hot water. There may also be mentioned, as coffeecomponent, coffee solutions prepared from concentrated coffee extract,soluble coffee obtained by drying coffee extract, or the like, withsuitable amounts of cold or hot water.

The cultivated species of coffee bean used as the raw material is notparticularly restricted, and there may be mentioned species such asArabica, Robusta, Liberica and the like, while the variety is also notparticularly restricted, and there may be mentioned Mocha, Brazil,Colombian, Guatemala, Blue Mountain, Kona, Mandelin, Kilimanjaro and thelike.

There are no particular restrictions on the degree of roasting(represented by the 3 basic levels of light roasted, medium roasted anddark roasted, in that order), and raw coffee beans may also be used.Coffee beans of two or more varieties may also be used in a blend.

There are also no particular restrictions on the degree of grinding ofthe roasted coffee beans (classified into coarse grinding, mediumgrinding, fine grinding, etc.), and ground coffee of different particlesize distributions may be used, while the extraction may be carried outwith any of various types of extractors (drip type, siphon type, boilingtype, jet type, continuous type, etc.) using cold water, hot water orthe like. A higher extraction temperature for the roasted coffee beansand a higher degree of extraction of the coffee component will tend topromote precipitation after heat sterilization, but there are noparticular restrictions on the temperature conditions or degree ofextraction.

The content of coffee component in the milk-added coffee beverage is notparticularly restricted, but is preferably 0.1-10 wt % in terms of solidportion. Here, “solid portion” refers to the weight of the dry materialobtained after drying the coffee component by a common drying method(lyophilization, evaporation to dryness, etc.) to remove the moisture.

In the present invention, “milk component” refers to a component addedto a coffee beverage in order to impart milk flavor or milk texture, andincludes primarily any milk, cow milk or dairy products. As examplesthere may be mentioned raw milk, cow milk, special cow milk, partiallydefatted milk, skim milk, processed milk, milk beverages and the like,and as dairy products there may be mentioned cream, concentrated whey,concentrated milk, concentrated skim milk, sugar-free condensed milk,sweetened condensed skim milk, total milk powder, skim milk powder,cream powder, whey powder, buttermilk powder, modified dry milk and thelike. Cow milk is preferably used from the standpoint of flavor.Fermented milk or lactic acid bacteria beverages may also be used in theform of powders.

The content of milk component in the milk-added coffee beverage is notparticularly restricted, but is preferably 0.1-10 wt % in terms of solidportion. Here, “solid portion” refers to the weight of the dry materialobtained after drying the milk component by a common drying method(lyophilization, evaporation to dryness, etc.) to remove the moisture.

In the present invention, a “strongly basic substance” is a substancesuch as a base or salt that is alkaline with a degree of electrolyticdissociation (α) of nearly 1 when dissolved in water. A value of α>0.9is preferred. The degree of electrolytic dissociation (α) is theproportion of the amount (moles, number of molecules) of ionized solute,where α=1 denotes complete ionization, or 100% ionization. As stronglybasic substances there may be mentioned sodium hydroxide, sodiumhydroxide solution, potassium hydroxide, potassium hydroxide solution,trisodium phosphate, tripotassium phosphate and the like.

The amount of strongly basic substance to be added is not particularlyrestricted, but is preferably 0.005-0.5 wt % in consideration of theeffect and cost. However, it is preferably added in an amount such thatthe pH of the milk-added coffee beverage does not rise aboveapproximately 8.0 after its addition.

Of the strongly basic substances according to the invention, sodiumhydroxide, (including sodium hydroxide solution), potassium hydroxide(including potassium hydroxide solution), trisodium phosphate andtripotassium phosphate are all food additives and are suitable for usefrom the standpoint of safety. These are available as commercialproducts in either solid or aqueous solution form. The purity is notparticularly limited so long as it is of a degree suitable forconsumption, and for example, the crystal sodium hydroxide purity may be70.0-75.0%, the sodium hydroxide anhydrate purity may be 95.0% orgreater and the potassium hydroxide purity may be 85.0% or greater. Thecrystallized form may be powdered, granular, globular, flaky,rod-shaped, etc. and is not particularly restricted.

In the invention, a “basic amino acid” is an amino acid that exhibitsbasicity in aqueous solution, and there may be mentioned lysine (Lys),arginine (Arg) and histidine (His). Salts, such as alkali metal salts oralkaline earth metal salts, or derivatives thereof which are basic andsuitable for consumption, are also included in the basic amino acids ofthe invention.

The amount of the basic amino acid to be added is not particularlyrestricted, but is preferably 0.01-1 wt % in consideration of effect andcost. Here it is also limited to an amount such that the pH of themilk-added coffee beverage does not rise above approximately 8.0 afteraddition.

Of the basic amino acids of the invention, lysine (L-lysine), arginine(L-arginine) and histidine (L-histidine) are all food additives and aresuitable for use from the standpoint of safety. These are available ascommercial products in either solid or aqueous solution form, and theirpurity is not particularly restricted.

The strongly basic substance and/or basic amino acid of the inventionmay be added at appropriate amounts in various combinations within arange that does not impair the anti-precipitation effect or flavor.

The strongly basic substance or basic amino acid is preferably added ina step after extraction of the coffee, i.e., before admixture of themilk component, but it may instead be preadded to the cold or hot waterused for the coffee extraction step.

The pH of the milk-added coffee beverage product is not particularlyrestricted, but in consideration of the object of the invention and theflavor of the beverage, the pH is preferably 5.8-7.0 for the productafter heat sterilization.

According to the invention, by using a strongly basic substance and/orbasic amino acid instead of sodium bicarbonate it is possible to reducethe amount of addition of emulsifier or thickening agent, which is acause of impaired flavor of milk-added coffee beverages. An “emulsifier”in the present invention is any additive with an emulsifying effect,which is a surfactant in the wide sense. As examples there may bementioned sucrose fatty acid esters, sorbitan fatty acid esters,polyglycerin fatty acid esters and the like. A “thickening agent” is anyadditive with a thickening, gelling or stabilizing function, and theremay be mentioned thickeners such as xanthan gum, gelling agents such ascarrageenan, and stabilizers. In other words, emulsifiers and/orthickening agents include all those commonly used to preventprecipitation that occurs primarily during the heat sterilization stepduring production of milk-added coffee beverages and in the subsequentdistribution, storage and vending machine warming.

Although an emulsifier or thickening agent is preferably used in thebeverage of the invention in order to supplement the anti-precipitationeffect, it is important for an amount added to be restricted to a rangethat does not notably impair flavor; and any emulsifiers and thickeningagents are preferably added in a total amount of no greater than 1 wt %.For example, sucrose fatty acid esters are often also used to preventproliferation of heat-resistant bacteria, and they may be added in arange that does not notably impair flavor. An emulsifier or thickeningagent may be added at any point with no particular restrictions, so longas it is added no later than immediately following the start of the heatsterilization.

Sodium bicarbonate may be added to the beverage of the invention inorder to complement the anti-precipitation effect during admixture ofthe milk component, but it is important for it to be in a range thatdoes not promote precipitation after heat sterilization, and the amountis preferably no greater than 0.14 wt %.

A “sweet component” according to the invention is any component thatexhibits sweetness. As examples, there may be mentioned sucrose,isomerized glucose, glucose, fructose, lactose, maltose, xylose,isomerized lactose, fructooligosaccharide, maltooligosaccharide,isomaltooligosaccharide, galactooligosaccharide, coupling sugar,paratinose, maltitol, sorbitol, erythritol, xylitol, lactitol,palatinit, reduced thickening agent sugar, stevia, glycyrrhizin,thaumatin, monellin, aspartame, alitame, saccharin, acesulfame K,sucralose, dulcin, and the like.

The presence, amount of addition and the point of addition of the sweetcomponent may be appropriately adjusted according to the designedproduct, and are not particularly restricted. For an enhancement offlavor, it is a preferred mode of the invention to either add no sweetcomponent or substantially no sweet component or to only lightly sweetenthe product, since this will allow the tongue to sense the originalflavor of the coffee with no influence of sweetening.

Other components may also be added, as appropriate, to impart to thebeverage of the invention the necessary or preferred properties as amilk-added coffee beverage. As other components there may be mentionedantioxidants, (sodium erythorbate, etc.), aromatics (coffee flavorings,milk flavorings, etc.) and water (ion-exchange water, purified water,natural water, etc.).

According to the invention, the heat sterilization method may involveretort sterilization, a hot pack, sterile packing or the like and is notparticularly restricted; while the sterilization conditions may beappropriately determined depending on the properties of the contents,the container, etc.

There are no particular restrictions on the shape of the container forthe milk-added coffee beverage, and it may be canned, PET bottled, glassbottled, cardboard packed, etc.

EXAMPLES

The invention will now be explained in greater detail by way ofexamples, with the understanding that the invention is in no wayrestricted to the examples.

Reference Example

The relationship between the amount of sodium bicarbonate addition andthe degree of precipitation after heat sterilization was examined underconditions with no emulsifier or thickening agent addition.

Sodium bicarbonate was added in different amounts to a coffee extract(pH: approximately 5.0) obtained by extraction of 12 g of roasted coffeebeans with purified water at 90° C., and then 12 g of sugar and 16 ml ofcow milk were added to obtain test solutions which were each adjusted toa total of 200 ml with purified water.

The amount of sodium bicarbonate addition was determined in thefollowing manner. For this test it was necessary to avoid precipitationduring addition of the cow milk (pH: approximately 6.6). Considering theisoelectric point of casein which constitutes half of the protein in cowmilk (near a pH of approximately 4.6), the addition of sodiumbicarbonate was set to the minimum giving a pH of 6.0 or greater beforethe cow milk addition for all of the test solutions (a finalconcentration of 0.33 g/L). Also, considering the pH range in which mostmilk-added coffee beverage products are distributed (a pH range ofapproximately 6.0-6.5, see arrow in FIG. 1), the amounts of sodiumbicarbonate were set to final concentrations of 0.33, 0.50, 0.67, 0.83,1.00, 1.17, 1.33, 1.67 and 2.00 g/L.

The obtained test solutions were filled into 190 g cans and subjected toheat sterilization (125° C., 20 minutes) to obtain canned milk-addedcoffee beverages without addition of emulsifier.

The degree of precipitation of each of the canned milk-added coffeebeverages was then measured by the following method. Specifically, thecanned milk-added coffee beverage was allowed to stand at roomtemperature for 3 hours and agitated, after which 10 ml thereof wassampled and dispensed into a graduated centrifugation tube andcentrifuged at 3000 rpm for 10 minutes, and the volume of theprecipitate was measured.

The results of the experiment are shown in FIG. 1. The horizontal axisrepresents the pH values of the (sterilized) canned milk-added coffeebeverages after addition of sodium bicarbonate at differentconcentrations (with a larger amount of sodium bicarbonate additionresulting in a higher pH).

As can be clearly seen from FIG. 1, under the pH conditions of this testwhich included the pH range in which most coffee beverage products aredistributed (a pH range of approximately 6.0-6.5, or in terms ofaddition of sodium bicarbonate, approximately 0.67-1.67 g/L; see arrowin FIG. 1), a strict correlation was found between the pH after heatsterilization (i.e. the amount of sodium bicarbonate addition) and thedegree of precipitation after heat sterilization. The degree ofprecipitation reached an acceptable level of under 0.1 ml/10 ml,depending on the amount of sodium bicarbonate addition (see pH range ofapproximately 6.0-6.2 in FIG. 1).

However, considering the fact that chemical changes during storage causeslight variation in the pH of milk-added coffee beverages, and the needto adapt to various product designs based on flavor, shelf life, etc., atechnique is required that can prevent precipitation under any pHcondition in the pH range of approximately 6.0-6.5 as the end product.The results of this test demonstrated that addition of sodiumbicarbonate alone, under conditions where no emulsifier or thickeningagent is added, can only be successfully applied in the limited pH rangementioned above.

Example 1

The use of sodium bicarbonate with different pH adjustors was examined.Sodium bicarbonate was added to coffee extract in a fixed amount, usingthe amount which produced the least precipitation in the experiment ofthe Reference Example (final concentration: 0.83 g/L, product pH: 6.2)(for a pH of 6.5 at this stage), and then different pH adjustors wereadded in amounts giving the same pH (pH 6.8). The procedure thereafterwas carried out according to the Reference Example to obtain cannedmilk-added coffee beverages.

Strongly basic substances (sodium hydroxide, potassium hydroxide) andweakly basic substances (disodium hydrogen phosphate, dipotassiumhydrogen phosphate, sodium bicarbonate (positive control)) were used asthe pH adjustors. Separately, a solution was prepared with purifiedwater added instead of a pH adjustor, as a negative control. The degreeof precipitation in each of the canned milk-added coffee beverages wasmeasured using the same method as in the Reference Example.

The results of this experiment are shown in FIG. 2. The pH values of thecanned milk-added coffee beverages fell after heat sterilization. Forexample, the test product to which sodium bicarbonate was added in theamount (0.83 g/L) which gave the lowest degree of precipitation had a pHof 6.2 (see FIG. 1), but its pH was 6.5 before heat sterilization. Thiswas thought to be due to a chemical change in the components by heating,and it is a phenomenon often seen upon heat sterilization of beverages.

As can be clearly seen from FIG. 2, the degree of precipitation changedsignificantly depending on the type of pH adjustor. Specifically, when astrongly basic substance (sodium hydroxide or potassium hydroxide) wasadded, the degree of precipitation was about as low as the negativecontrol (purified water). On the other hand, when a weakly basicsubstance (disodium hydrogen phosphate, dipotassium hydrogen phosphateor sodium bicarbonate (positive control)) was added, the degree ofprecipitation was greater than when a strongly basic substance wasadded.

It was thus demonstrated that to control precipitation of milk-addedcoffee beverages during heat sterilization, it is effective to replace aportion of the sodium bicarbonate used as a pH adjustor with a differentpH adjustor, and particularly that the use of a strongly basic substancesuch as sodium hydroxide or potassium hydroxide is important.

Example 2

Based on the knowledge obtained from Example 1, all of the sodiumbicarbonate was replaced with a strongly basic substance (sodiumhydroxide in this case). In the same manner as the Reference Example,the sodium hydroxide concentration was added in different amounts toobtain canned milk-added coffee beverages with no emulsifier added. Theresults of the experiment are shown in FIG. 3.

As can be clearly seen from FIG. 3, when all of the sodium bicarbonatewas replaced with a strongly basic substance, a notable effect ofpreventing precipitation was found in the pH range in which commonmilk-added coffee beverage products are distributed (a pH range ofapproximately 6.0-6.5, see arrow in FIG. 3).

It was thus demonstrated that to control precipitation of milk-addedcoffee beverages during heat sterilization, it is effective to use astrongly basic substance alone as the pH adjustor. It was alsodemonstrated that using a strongly basic substance as the pH adjustorcan prevent precipitation during heat sterilization under any pHcondition in the pH range of approximately 6.0-6.5 as the end product.

Example 3

A test sample of a milk-added coffee beverage (emulsifier-free) wasprepared by mixing the raw materials in the prescribed amounts shown inTable 1, heat sterilizing and adding a strongly basic substance, and thedegree of precipitation and flavor were evaluated (Test Product 1). Twocontrol test samples of sodium bicarbonate-containing milk-added coffeebeverages (Control Product 1-1: emulsifier-free product and ControlProduct 1-2: emulsifier-added product) were also prepared. An emulsifier(sucrose fatty acid ester) was added to Control Product 1-2 in thenecessary amount as an anti-precipitation agent.

Table 2 shows the evaluation results for the degree of precipitation andthe flavor. The degree of precipitation was measured according to theReference Example. The flavor was evaluated as the average of score byfive professional panelists. Scoring was on the following 5 levels:“Good”=5 points, “Fair”=4 points, “Ordinary”=3 points, “Somewhat poor”=2points, “Poor”=1 point.

The results are shown in Table 2. The flavor evaluation score for TestProduct 1 (sodium bicarbonate-added, emulsifier-free) was fair at 4.2,but the degree of precipitation was 0.70 ml/10 ml, which wasconsiderably greater than the target value (≦0.1 ml/10 ml).

With Control Product 1-2 (sodium bicarbonate-added, emulsifier-added),the effect of adding the emulsifier reduced the degree of precipitationto 0.05 ml/10 ml which was an acceptable level (less than 0.1 ml/10 ml).However, the flavor evaluation score (3.0) was lower than that of theother two products (4.2-4.6), suggesting that addition of the emulsifierled to a reduction in flavor.

On the other hand, the degree of precipitation with Control Product 1was at an acceptable level of 0.05 ml/10 ml (less than 0.1 ml/10 ml),while the flavor evaluation score of 4.6 was the highest evaluationamong the three products. This indicates that precipitation wassuccessfully inhibited without using an emulsifier that causes reductionin flavor.

Thus, by using the present invention which employs a strongly basicsubstance as the pH adjustor, it is possible to inhibit precipitationduring heat sterilization and produce a milk-added coffee beverage witha satisfactory taste.

TABLE 1 Control Control Test Product 1-1 Product 1-2 Product 1 Coffeebeans 60 g 60 g 60 g Sugar 60 g 60 g 60 g Sodium bicarbonate 2.0 g 2.0 g0 g Sodium hydroxide 0 g 0 g 0.4 g Emulsifier 0 g 1.5 g 0 g Cow milk 120ml 120 ml 120 ml Total (adjusted with water) 1000 ml 1000 ml 1000 ml

TABLE 2 Control Control Test Product 1-1 Product 1-2 Product 1 Degree ofprecipitation 0.70 0.05 0.05 (ml/10 ml) Average score of 4.2  3.0  4.6 flavor evaluation

Example 4

Next, basic amino acids were examined as additives expected to providean anti-precipitation effect, in addition to the strongly basicsubstances which were confirmed to have a high anti-precipitationeffect.

Emulsifier-free canned milk-added coffee beverages were obtained in thesame manner as the Reference Example, but using only a basic amino acid(arginine or histidine) as the pH adjustor. As a control, a test sampleof an emulsifier-free canned milk-added coffee beverage was obtainedusing only sodium bicarbonate as the pH adjustor. The results of theexperiment are shown in FIG. 4.

As can be clearly seen from FIG. 4, the degree of precipitation was anacceptable level (≦0.1 ml/10 ml) when using either basic amino acid, andmuch lower than sample using sodium bicarbonate as the pH adjustor. Themethod of using a basic amino acid as the pH adjustor was thusdemonstrated to be useful for inhibiting precipitation during heatsterilization of milk-added coffee beverages.

Example 5

Raw materials were combined in the prescribed amounts shown in Table 3and heat sterilized, and then a strongly basic substance was added toprepare a milk-added coffee beverage (emulsifier-free) as a coffee- andcow milk-augmented type test product, and the degree of precipitationand flavor were evaluated. As a control, a coffee- and cowmilk-augmented type test product was prepared by adding sodiumbicarbonate to a milk-added coffee beverage (emulsifier-added). Anemulsifier (sucrose fatty acid ester) was added thereto in the necessaryamount as an anti-precipitation agent.

The degree of precipitation was measured according to the ReferenceExample, and the flavor evaluation was carried out according to Example3. Table 4 shows the degrees of precipitation and the results of theflavor evaluation.

TABLE 3 Control Test Product 2 Product 2 Coffee beans 75 g 75 g Sugar 60g 60 g Sodium bicarbonate 2.5 g 0 g Sodium hydroxide 0 g 0.5 gEmulsifier 3.0 g 0 g Cow milk 150 ml 150 ml Total (adjusted with water)1000 ml 1000 ml

TABLE 4 Control Product 2 Test Product 2 Degree of precipitation 0.070.06 (ml/10 ml) Average score of 2.8  4.6  flavor evaluation

As shown in Table 4, the degree of precipitation of Test Product 2 wasat an acceptable level (<0.1 ml/10 ml), equivalent to that of ControlProduct 2. However, the flavor evaluation of Test Product 2 was higherthan that of the control product. It is presumed that with the highcoffee and cow milk content in Control Product 2, the flavor evaluationwas unsatisfactory because of the increase in emulsifier necessary toprevent precipitation after heat sterilization, whereas even with a highcoffee and cow milk content in the Test Product 2, a satisfactory flavorevaluation was obtained because precipitation after heat sterilizationwas successfully prevented without addition of an emulsifier.

Example 6

A test sample of a milk-added coffee beverage (emulsifier-free)containing both a strongly basic substance and a basic amino acid wasprepared by mixing the raw materials in the prescribed amounts shown inTable 5 and heat sterilizing.

As a result, the degree of precipitation of Test Product 3 was at anacceptable level (≦0.1 ml/10 ml), and the flavor evaluation wassatisfactory.

Thus, by using the present invention which employs a basic amino acid asthe pH adjustor, it is possible to inhibit precipitation during heatsterilization and produce a milk-added coffee beverage with asatisfactory taste.

TABLE 5 Test Product 3 Coffee beans 60 g Sugar 60 g Sodium hydroxide 0.2g Arginine 0.6 g Cow milk 120 ml Total (adjusted with water) 1000 ml

Example 7

The effect of the invention when adding no sweet components wasevaluated.

A milk-added coffee beverage (emulsifier-free) containing no sweetcomponent, using a strongly basic substance as the pH adjustor, wasprepared as a test sample with the raw materials in the prescribedamounts shown in Table 6, and the degree of precipitation and flavorwere evaluated. A test product of a milk-added coffee beverage(emulsifier-added) containing no sweet component and using sodiumbicarbonate as the pH adjustor was also prepared as a control. Anemulsifier (sucrose fatty acid ester) was added thereto in the necessaryamount as an anti-precipitation agent.

The degree of precipitation was measured according to the ReferenceExample, and the flavor evaluation was carried out according to Example3. Table 7 shows the degrees of precipitation and the results of theflavor evaluation.

TABLE 6 Control Test Product 4 Product 4 Coffee beans 60 g 60 g Sodiumbicarbonate 2.0 g 0 g Sodium hydroxide 0 g 0.4 g Emulsifier 2.5 g 0 gCow milk 120 ml 120 ml Total (adjusted with water) 1000 ml 1000 ml

TABLE 7 Control Product 4 Test Product 4 Degree of precipitation 0.060.05 (ml/10 ml) Average score of 2.3  4.8  flavor evaluation

As a result, the degree of precipitation of the test product and of thecontrol product were both equivalent at an acceptable level (≦0.1 ml/10ml). However, the flavor evaluation of the test product was higher thanthat of the control product. The difference in the flavor evaluations ofboth products was greater than in the previous test (Example 3) in whichsweetness was added. It is presumed that when no sweet component isadded, the flavor can be judged without the influence of sweetness,allowing a more definite distinction between rich and poor flavor.

Thus, the present invention can be suitably used when the flavor is tojudged without the influence of sweetness, such as in cases withsubstantially no addition of sweet components or with only lightsweetening.

1. A method for suppressing the formation of precipitates to less than 0.1 ml per 10 ml during heat sterilization in producing a milk-added and heat-sterilized coffee beverage which comprises a coffee component in terms of solid portion from 1.08 to 10 w/v%, and a milk component in terms of solid portion from 1.48 to 10 w/v%, wherein; the method comprises adding 0.005-0.5 w/v% of sodium hydroxide or a combination of sodium hydroxide and potassium hydroxide to a coffee component, in addition to from 0 to less than 0.14 w/v% sodium bicarbonate, and an emulsifier and a thickening agent in total of less than 1 w/v%; adding a milk component to the coffee component; and heat-sterilizing the mixture.
 2. A method according to claim 1, wherein the pH of the heat-sterilized beverage is 5.8-7.0.
 3. A method according to claim 1, wherein a combination of sodium hydroxide and potassium hydroxide is added.
 4. A method according to claim 1, wherein only sodium hydroxide is added.
 5. A method according to claim 1, wherein the sodium hydroxide or combination of sodium hydroxide and potassium hydroxide is added in an amount such that the pH of the beverage does not rise above 8.0 before the heat-sterilization.
 6. A method according to claim 1, wherein the milk component is cow's milk.
 7. A milk-added and heat-sterilized coffee beverage comprising from 1.08 to 10 w/v % of a coffee component in terms of solid portion, from 1.48 to 10 w/v % of a milk component in terms of solid portion, less than 1 w/v % in total amount of an emulsifier and thickening agent, from 0 to less than 0.14 w/v % of sodium bicarbonate, and 0.005-0.5 w/v % of at least one strongly basic substance selected from the group consisting of sodium hydroxide and a combination of sodium hydroxide and potassium hydroxide, wherein the amount of precipitates in the beverage formed due to heat-sterilization is less than 0.1 ml/10 ml.
 8. A beverage according to claim 7, wherein the strongly basic substance is a combination of sodium hydroxide and potassium hydroxide.
 9. A beverage according to claim 7, wherein the strongly basic substance is sodium hydroxide.
 10. A beverage according to claim 7, wherein the pH of the beverage after heat-sterilization is in a range between 5.8 and 7.0.
 11. A beverage according to claim 7, which further comprises one or more optional ingredients selected from sweet components, antioxidants and flavorings.
 12. A beverage according to claim 7, wherein the milk component is cow's milk.
 13. A beverage according to claim 7, which is packaged in a hermetically sealed container. 